Field of the Invention
The present invention relates to a three-dimensional measurement apparatus for capturing images of a workpiece from two or more view points to make a three-dimensional measurement or view the workpiece stereoscopically, and a robot system including the same.
Description of the Related Art
Conventionally, as a method of measuring the three-dimensional shape of a workpiece in a non-contact manner, a stereo method has been known, in which the workpiece is captured from cameras located at two or more view points to measure a three-dimensional shape of the workpiece from the captured two or more images. In the stereo method, edge lines of the workpiece on the captured images may be used to measure the three-dimensional shape of the workpiece with a small amount of information.
The stereo method for measuring the three-dimensional shape using edge lines can obtain an exact three-dimensional shape of the workpiece under ideal conditions, but there is an error in calibrating a camera or an error in extracting an edge line in practice. This causes a problem that edge lines that should have been connected are recreated in twisted positions or the angle between edge lines is inaccurate in the measured three-dimensional shape.
In contrast to this, there is proposed a technique for using a condition that a plurality of edge lines of a workpiece lies on the same plane (hereinafter called “plane constraint condition”) to correct a corresponding point in order to improve the accuracy of three-dimensional measurement (see Japanese Patent Application Laid-Open No. 2003-248814).
However, in the technique disclosed in Japanese Patent Application Laid-Open No. 2003-248814, the plane constraint condition that a group of points on the same plane should meet to determine a plane parameter in order to correct a corresponding point on an image. Therefore, multiple three-dimensional constraint conditions, such as a relative angle between edge lines that do not lie on the same plane and a stereoscopic positional relationship between edge lines, cannot be added.
When three-dimensional data is actually generated from captured images, it is often the case that multiple three-dimensional constraint conditions, such as “edge lines are perpendicular to each other”, “edge lines are parallel to each other”, and “edge lines lie on the same straight line”, are already known by design. Therefore, a three-dimensional measurement apparatus is desired, which applies these multiple three-dimensional constraint conditions to improve the accuracy of three-dimensional measurement.
The present invention provides a three-dimensional measurement apparatus capable of measuring a highly accurate three-dimensional shape and a robot system including the same.